Thermostatic control for use in variable air distribution systems

Abstract

Air flow volume in a delivery duct is sensed in the form of changes in duct pressure and the sensed pressure is fed back to a diaphragm assembly which is part of a thermostatic control located in the room to which hot or cold air is being delivered. Dependent upon the sensed pressure, the diaphragm assembly throttles a bleed opening in the supply line of a pneumatic actuator, which actuator determines the position of a damper in the duct to thereby control the volume of air flow in the duct. A bellows is also part of the thermostatic control and senses room temperature to establish a spring force on the diaphragm assembly and against which the sensed pressure must act. The bellows is adjustable to afford room temperature selection. The bellows and a compression spring act on a master lever, the compression spring reacts against the bellows force. The combination bellows-spring produces movement of the master lever in two opposite directions and this movement is utilized to activate a control for continuously switching the system between delivery of cold or hot air. The thermostatic control includes a second lever moved in response to the bellows-spring movement. The position of the second lever establishes a biasing force against which, in the diaphragm assembly, the sensed duct pressure must act in establishing the position of the damper. A cam arrangement is associated with this second lever and is effective to determine the position, and movement, of the lever so as to provide selection in the percent of available air capacity which is utilized and/or lever movement between maximum and minimum limits as desired.

We claim: 
     
       1. In an air delivery system including duct means for delivering air to an area being serviced, means for supplying air to said duct means, damper means in said duct means and mounted to assume any one of a number of available positions in said duct means for controlling the volume of air flowing therethrough, actuator means connected to and operative to move said damper means selectively to one of said positions; the improvement of temperature and pressure responsive control means positioned in the area being serviced and comprising, in combination, pressure responsive means connected to and controlling the operation of said actuator means,   means connecting said pressure responsive means for exposure thereof to the interior of said duct means so that said pressure responsive means controls said actuator means in accordance with the pressure condition in said duct means,   said pressure responsive means including biasing means producing a bias force reacting against the pressure condition to which said pressure responsive means is exposed,   and temperature responsive means engaging said biasing means and influencing the magnitude of said bias force and operative to establish bias forces in accordance with the temperature ambient said temperature responsive means so that the position of said damper means in said duct means is determined by the reaction between said biasing means and the pressure condition in said duct means and said pressure responsive means controls said actuator means and in turn said damper means to maintain the volume of flow through said duct substantially constant.   
     
     
       2. The combination of claim 1 wherein said temperature responsive means is adjustable to select a particular ambient temperature. 
     
     
       3. The combination of claim 1 wherein said pressure responsive means comprises a diaphragm and said biasing means produces said bias force on said diaphragm,   and including means in said duct means for sensing the pressure in said duct means and transmitting said sensed pressure to said diaphragm.   
     
     
       4. The combination of claim 1 wherein said control means includes a base,   said pressure responsive means includes means defining two chambers in said base and a diaphragm separating said chambers,   means in said duct means for sensing duct pressure and connected to said chambers to produce a pressure differential across said diaphragm,   and wherein said biasing means is connected to said diaphragm.   
     
     
       5. The combination of claim 4 wherein said actuator is pneumatically operated,   a source of air is connected to and is operative to energize said actuator,   a bleed port is included in the connection of said air source to said actuator through which air can be bled to control actuator operation,   plug means positioned at said bleed port and connected to and movable with said diaphragm relative to said bleed port to vary the amount of air being bled through said port.   
     
     
       6. In an air delivery system including duct means for delivering air to an area being serviced, means for supplying air to said duct means, damper means in said duct means and mounted to assume any one of a number of available positions in said duct means for controlling the volume of air flowing therethrough, actuator means connected to and operative to move said damper means selectively to one of said positions; the improvement of temperature and pressure responsive control means positioned in the area being serviced and comprising, in combination, a base,   pressure responsive means connected to and controlling the operation of said actuator means, said pressure responsive means including means defining two chambers in said base and a diaphragm separating said chambers,   means in said duct means for sensing duct pressure and connected to said chambers to produce a pressure differential across said diaphragm so that said pressure responsive means is exposed to the interior of said duct means and said pressure responsive means controls said actuator means in accordance with the pressure condition in said duct means,   said pressure responsive means also including biasing means connected to said diaphragm and producing a bias force reacting against the pressure condition to which said pressure responsive means is exposed,   temperature responsive means comprising a charged bellows,   means connecting said bellows to said base,   and lever means connecting said bellows to said biasing means so that the bias force generated by said biasing means is varied in accordance with the expansion and contraction of said bellows and in accordance with the temperature ambient said bellows   whereby said temperature responsive means is connected to said biasing means and influences the magnitude of said bias force and is operative to establish bias forces in accordance with the temperature ambient said temperature responsive means so that the position of said damper means in said duct means is determined by the reaction between said biasing means and the pressure condition in said duct means and said pressure responsive means controls said actuator means and in turn said damper means to maintain the volume of flow through said duct substantially constant.   
     
     
       7. The combination of claim 6 wherein said actuator is pneumatically operated,   a source of air is connected to and is operative to energize said actuator,   a bleed port is included in the connection of said air source to said actuator through which air can be bled to control actuator operation,   plug means positioned at said bleed port and connected to and movable with said diaphragm relative to said bleed port to vary the amount of air being bled through said port.   
     
     
       8. In an air delivery system including duct means for delivering air to an area being serviced, means for supplying air to said duct means, damper means in said duct means and mounted to assume any one of a number of available positions in said duct means for controlling the volume of air flowing therethrough, actuator means connected to and operative to move said damper means selectively to one of said positions; the improvement of temperature and pressure responsive control means positioned in the area being serviced and comprising, in combination, pressure responsive means connected to and controlling the operation of said actuator means,   means connecting said pressure responsive means for exposure thereof to the interior of said duct means so that said pressure responsive means controls said actuator means in accordance with the pressure condition in said duct means,   said pressure responsive means including biasing means producing a bias force reacting against the pressure condition to which said pressure responsive means is exposed,   temperature responsive means,   lever means connecting said temperature responsive means to said biasing means,   said temperature responsive means producing motion of said lever in one direction in response to an increase in temperature ambient said temperature responsive means and an opposite direction in response to a decrease in said ambient temperature,   whereby said temperature responsive means is connected to said biasing means and influences the magnitude of said bias force and is operative to establish bias forces in accordance with the temperature ambient said temperature responsive means so that the position of said damper means in said duct means is determined by the reaction between said biasing means and the pressure condition in said duct means and said pressure responsive means controls said actuator means and in turn said damper means to maintain the volume of flow through said duct substantially constant,   and reheat means adjacent to and engageable by said lever means, said reheat means connected to and operative to actuate means for switching said air delivery system from a heating cycle to a cooling cycle;   said reheat means having a normal position establishing one of said cycles and being moved from said normal position by said lever means to establish the other cycle.   
     
     
       9. The combination of claim 8 wherein said pressure responsive means includes a diaphragm,   including means in said duct means for sensing duct pressure and connected to said diaphragm to produce a pressure differential across said diaphragm,   wherein said biasing means is connected to said diaphragm,   wherein said temperature responsive means comprises a charged bellows,   and wherein said lever means connects said bellows to said biasing means so that the bias force generated by said biasing means is varied in accordance with the expansion and contraction of said bellows in accordance with the temperature ambient said bellows.   
     
     
       10. The combination of claim 9 including means for adjusting the bias force produced by said biasing means acting against said bellows. 
     
     
       11. The combination of claim 9 wherein said lever means includes first and second levers,   wherein said bellows engages said first lever,   including biasing means engaging said first lever and producing a bias force against which said bellows expands, said first lever being moved in one direction by bellows expansion and in an opposite direction by said biasing means as said bellows contracts,   said first lever being engageable with said reheat means,   and wherein said second lever connects said first lever to said biasing means producing the bias force on said diaphragm.   
     
     
       12. In an air delivery system including duct means for delivering air to an area being serviced, means for supplying air to said duct means, damper means in said duct means and mounted to assume any one of a number of available positions in said duct means for controlling the volume of air flowing therethrough, actuator means connected to and operative to move said damper means selectively to one of said positions; the improvement of temperature and pressure responsive control means positioned in the area being serviced and comprising, in combination, pressure responsive means connected to and controlling the operation of said actuator means,   means connecting said pressure responsive means for exposure thereof to the interior of said duct means so that said pressure responsive means controls said actuator means in accordance with the pressure condition in said duct means,   said pressure responsive means including biasing means producing a bias force reacting against the pressure condition to which said pressure responsive means is exposed,   temperature responsive means,   lever means connecting said temperature responsive means to said biasing means and through which said temperature responsive means operates on said biasing means to influence the magnitude of said bias force and is operative to establish bias forces in accordance with the temperature ambient said temperature responsive means so that the position of said damper means in said duct means is determined by the reaction between said biasing means and the pressure condition in said duct means and said pressure responsive means controls said actuator means and in turn said damper means to maintain the volume of flow through said duct substantially constant,   first and second cam members each including a groove disposed at an oblique angle to the axis along which said biasing means acts, said grooves being complementary and when registered defining a notch at said oblique angle,   a projection on said lever means extending into said notch,   and means mounting said first and second cam members for joint and relative movement to establish a preselected position of said lever means.   
     
     
       13. The combination of claim 12 wherein said cam members are generally cylindrical and said grooves are provided in the periphery of said cam members and said grooves are at an oblique angle to a radial plane perpendicular to the axis of said cam members,   including a scale mounted adjacent said cam members and calibrated in percentage of available air delivery capacity,   and pointers on each of said cam members associated with said scale.   
     
     
       14. The combination of claim 13 wherein said pressure responsive means comprises a diaphragm and said biasing means produces said bias force on said diaphragm,   and including means in said duct means for sensing the pressure in said duct means and transmitting said sensed pressure to said diaphragm.   
     
     
       15. The combination of claim 14 wherein said actuator is pneumatically operated,   a source of air is connected to and is operative to energize said actuator,   a bleed port is included in the connection of said air source to said actuator through which air can be bled to control actuator operation,   plug means positioned at said bleed port and connected to and movable with said diaphragm relative to said bleed port to vary the amount of air being bled through said port.   
     
     
       16. The combination of claim 15 wherein said control means includes a base,   said pressure responsive means includes means defining two chambers in said base and a diaphragm separating said chambers,   means in said duct means for sensing duct pressure and connected to said chambers to produce a pressure differential across said diaphragm,   and said biasing means is connected to said diaphragm.